The floating particles produced by the excitation discharge for TEA gas laser have been visualized by the pulsed-laser reflection method. The double-pulse discharge experiments have also been carried out to study the effects of the floating particles on the discharge instabilities. Two kinds of gas mixture are used to simulate KrF excimer laser; F2/Kr/He/Ne (gas A) and Kr/He/Ne (gas B). The particles with diameter of the order of 100 jtm are observed in the discharge region. In both gas mixture, the number density ofthe particles increases to ~ 3 particle/cm3 at 200 ms after the discharge, and then decreases to ~ 1 particle/cm3 at 500 ms. On the other hand, the double-pulse discharge characteristics are very different between gases A and B. In the gas A, the second discharge tends to be an arc when the pulse interval decreases to 300 ms. However, the arc does not occur in the gas B. It is deduced that the floating particles of the order of 100 ?m in diameter do not strongly affect the discharge instabilities.